In the past, flexural pivots which support oscillating shaft assemblies have suffered damage from dynamic loads which were experienced during transport. Where the shaft movements have critically close tolerances, even moderate dynamic loads can cause catastrophic failure.
In optical scientific instruments, scanning mirrors are mounted on a shaft having a limited rotation. These shafts, called flexural pivots, because of their light torsional spring rates and low radial load carrying capabilities are selected where power is limited. Further information about flexural pivots may be found in U.S. Pat. Nos. 3,807,029 and 3,811,665. If the optical instruments, such as earth sensors or horizon scanners are used in space vehicles, severe dynamic loads, such as vibration and shock induced by the booster during launch, will sometimes buckle or fracture the flexing elements causing catastrophic failure. For this reason, such instruments are commonly equipped with a caging device for caging or clutching the rotatable member or shaft to the instrument housing to restrain the shaft against rotation.